400010021 has 16 divisors (see below), whose sum is σ = 437006400. Its totient is φ = 365707440.

The previous prime is 400009999. The next prime is 400010057. The reversal of 400010021 is 120010004.

It is a de Polignac number, because none of the positive numbers 2^k-400010021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 400009990 and 400010008.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (400010921) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 197906 + ... + 199916.

It is an arithmetic number, because the mean of its divisors is an integer number (27312900).

Almost surely, 2^400010021 is an apocalyptic number.

It is an amenable number.

400010021 is a deficient number, since it is larger than the sum of its proper divisors (36996379).

400010021 is an equidigital number, since it uses as much as digits as its factorization.

400010021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2097 (or 2059 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 8.

The square root of 400010021 is about 20000.2505234310. The cubic root of 400010021 is about 736.8124526233.

Adding to 400010021 its reverse (120010004), we get a palindrome (520020025).

The spelling of 400010021 in words is "four hundred million, ten thousand, twenty-one".